Several people have asked for a clear statement from Silicon Graphics
about the openness of Inventor's file format. This is the statement,
created by Rikk Carey (the project leader of the Inventor group at
Silicon Graphics) and Gavin Bell (one of the engineers in the Inventor
group).
Silicon Graphics wants the Inventor file format to become the standard
for 3D object and scene exchange. The VRML effort is very exciting,
and has the possibility of becoming a widespread format for 3D scenes;
we want the VRML format to be a subset+extension of Inventor's file
format.
We encourage the creation of parsers, converters and tools that work
with the Inventor file format, on any type of computer, whether
manafactured by Silicon Graphics or not. Inventor's ASCII file format
is truly open, freely usable by anybody, in whole or part.
We assume users of the format will make changes to it in a compatible
way. The format has a very well-defined syntax for the compatible
addition of new objects; we want to discourage users from making
incompatible changes to the existing, defined Inventor objects. For
example, if you are tempted to add extra information to Inventor's
Sphere object, please create a new object with a new name
("SphereExt") to avoid compatibility problems for users. However, we
are not interested in using legal action to try to enforce
compatibility; we believe that the incentive to be compatible with
existing Inventor applications will be enough to prevent this.
While we reserve the right to make changes to the core Inventor
format, we do not expect to make any such changes in the near future.
Every Inventor file is required to have a header line identifying the
version of the format; we will not make changes to the core format
without incrementing the format version number in the header.
Inventor also has a binary file format that is not documented and is
intended to be read and written only by applications using the
Inventor library. The only real advantage that the binary format has
over the ASCII format is that reading a binary file is faster, since
less parsing must be done. Binary files are about the same size as
compressed (using any of the popular compression utilites) ASCII
files, so transfer time should not be a reason to want to use the
binary format. We do not intend to make the binary format open.
Note that the names "IRIS Inventor" and "Open Inventor" are trademarks
of Silicon Graphics, and Silicon Graphics will protect those
trademarks. In other words, feel free to create a parser for the
Inventor ASCII file format, just don't call that parser "Open
Inventor". We do encourage you to advertise the fact that your
products read and/or write the Inventor file format.
And finally, we (Rikk and Gavin) don't feel like we are legally
competent enough to use the term "public domain". Hopefully, this
statement is enough to quell any fears of legal action from SGI if
Inventor's file format is used as the basis for VRML.